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I understand if the main reason for LEDs is better looking lighting. I especially like the way the warm white appears.

But, just a couple points. I run both straight conventional and conventional in command mode with Post War and MPC passenger trains and twin AC motored dual power units. I would like constant voltage lighting for these, but I wouldn't want to convert two whole trains to LEDs if in the end I still can't get constant voltage.

What would be the answer?

Secondly, about the reduction in current draw I've seen talked about here. I run 135 watt PHs and have NEVER had a lack of current problem with any consist at any speeds for any distance. However I can see that the very few with very large layouts trying to run more than one train on one loop might get into something like that.

In any event, is there really a legit need across the board for a reduction in current? Is it really that big a problem in the first place with what most of us are doing?
Hello Ginsaw
Great questions. The boards being discussed in this thread are not for conventional layouts, only for Command, Legacy or DCS layouts that operate with constant track voltage of 18 to 20 volts. Small layouts probably don't usually use up most of the power supplied. Power becomes an issue when running multiple engines at the same time and long passenger trains.
The second issue is how realistic does a person want their passenger trains to look. These boards achieve whatever level of realism a person wishes to attain. Good marker lights, rear beacon, drum head lights, vestibule lighting, lit candles on each dining car table no flickering and realistic interior lights color and intensity is achievable if a person wishes it, but that is not what everyone wants. These boards are not essential for operating and having fun with a layout. These boards are intended for those people who would like to take their layout to a different level. Jack
quote:
Originally posted by Ginsaw:
I understand if the main reason for LEDs is better looking lighting. I especially like the way the warm white appears.

But, just a couple points. I run both straight conventional and conventional in command mode with Post War and MPC passenger trains and twin AC motored dual power units. I would like constant voltage lighting for these, but I wouldn't want to convert two whole trains to LEDs if in the end I still can't get constant voltage.

What would be the answer?

Secondly, about the reduction in current draw I've seen talked about here. I run 135 watt PHs and have NEVER had a lack of current problem with any consist at any speeds for any distance. However I can see that the very few with very large layouts trying to run more than one train on one loop might get into something like that.

In any event, is there really a legit need across the board for a reduction in current? Is it really that big a problem in the first place with what most of us are doing?


You can get constant voltage lighting with a 7805 regulator circuit or a current limiting chip. These circuits will work in conventional or command. The circuit is drawn in a post I linked earlier.

Dale H
quote:
Originally posted by gunrunnerjohn:
Well, I was looking at this one.

Passenger Car Lighting

It's hard to read the schematic, and I don't see a part number specified for what you're calling a constant current chip. Is that just something like the LM317 wired for constant current?


The P/N is CL2-N3. It is not a voltage regulator,it is a current regulator chip. When voltage is feed in 5-18 volts DC only 20ma goes through the chip. The 20 ma is what is needed for many LEDS. So if one is circuited to each LED it gives constant voltage lighting for conventional operators like me. The chip takes the place of a current limiting resistor. Since it is a current limiter it acts as a variable resistor as input voltage is changed. It can also drive LEDs in series for command operators or building lighting applications etc and eliminates the need for resistor calculation. The chip can handle about 1/2 watt.

The chip is pictured at the latter part of this thread for caboose lighting in the TO92 package. Other packages are offered.

http://www.jcstudiosinc.com/Bl...d=487&categoryId=426

The chip is available from Mouser. If you click on the data sheet the circuiting is described in PDF form.

http://www.mouser.com/Search/R....aspx?Keyword=cl2-n3

Dale H
Oh yeah, one other thing that I like about the Jack Pearce board is the ability to connect up to seven additional LEDs directly to the board for drumheads, marker lamps, etc. This eliminates the need to install additional electronic components. I plan to replace the GGD LED strips in my observation cars with one of these and I will install the GGD strip in another car.
I just picked up a set of MTH Southern Pacific Daylight passenger cars (HO), I placed them on the tracks and there was a one minute delay in the LED lighting. I read the manual and found out they have a capacitor, the lighting is flicker free.
Does anyone know if the New MTH O gauge cars have these features?
Wait till you see the new LED lighting MTH is now using in their HO passenger cars! They have added a capacitor to the circuit so that it takes about 3 to 5 minutes befor the lights come on, after track power is supplied. The result?

ABSOLUTELY NO LIGHT FLICKERING!!!!!

The MTH Research & Development Dept. is working on trying to put the same system, including the newer "softer lighting" LEDs, in our O Gauge 3-Rail passenger cars and cabooses.
quote:
Originally posted by DaveJfr0:
I hate to bring this back up, but I just tried to rewire an MTH amfleet car for LED operation using diodes instead of a full wave rectifier. Half the cars will have the diode facing one way, the other half facing the other way, so it essentially pulls the full wave after 2 cars.


Basically trying to take half-wave of the AC at about 18 VAC and pass it through to the DC side. I assume I need one more diode before ground with the + end facing the - side of the cap…is this correct? That way the AC signal can't come back into the DC side of the circuit? I know AC doesn't really have +/-, so think of them as one going to the center pickup roller and one going to the wheels.


A picture of the diagram with the potentially added diode that I am not sure about is here:

Also, should the choke be on the AC side of the diode? Does it matter? They do not teach practical uses of inductors at the university I went to, so that part is confusing.


It seems I should have just used a FWR chip and called it a day, but I wanted to learn how to wire a HWR circuit like this.


Unless I am missing something here, with the 1N4006 oriented as it is, I believe the capacitor will will have a negative voltage on its + terminal, not good. I would suggest turning the 1n4006 opposite way. Led have a low reverse voltage breakdown. It is generally not good practice to subject them to the reverse voltage as it would be in this hookup. By turning the diode 180 degrees, it will effectivly block the reverse voltage and let the full half wave light the LEDs.

While the idea of half your cars working one side of the AC waveform and the others the other hald I am not sure you are really gaing that much, plus try to keep the number of cars "balanced" with positive and negative connected cars.

My 2 cents.
quote:
I'm using a massive cap (.25/each) myself


Are you using a supercapacitor? These generally have a very low voltage rating.

Your original drawing is indeed wrong, with the diode pointing the wrong way.

To limit the surge current through the inductor, you may want to move some or all of the 550 ohm resistor value to be in series with the diode before the capacitor.

Two diodes as Dale H. suggested will protect the jumper wire between the two trucks in case one roller lands on the outer rail and the other roller is still on the center rail.
quote:
Originally posted by DaveJfr0:
It looks like I'll go ahead and switch over a to a 2-diode protection system. By moving the Resistor from the LED branch over to the diode branch, it would also reduce the maximum voltage that cap could charge to, correct (not that I think it will seriously matter in this case)?


The resistor also eases the current turn on surge of the cap charging up. Although 1000uF is not that big it does reduce the stress across the diode taking the brunt of the initial current until the cap gets charged up.
In your original single-diode configuration (wired backwards), the capacitor might have exploded which can be violent. The choke acted as a fuse so consider yourself lucky.

If you flip the diode, or use any of the other configurations suggested, the inductor will be fine. Per the eBay spec, if your LEDs draw, say, 20 milliAmps on average, the inductor will only dissipate about 1 milliWatt which you won't feel by touching it.
Dale, the choke needs to separate the track from the AC-bypassing effect of the capacitor. It should be either "before" or "after" the capacitor in the ciruit loop. (The DCS signal uses the center and outer rails as two conductors to form a loop through the locomotive. If the capacitor shorts out the AC component of this signal by bridging from center to outer rail, the DCS will be attenuated. The only good factor is that the electrolytic capacitor is probably not working very well as a shunt at 900 MHz due to its internal inductance.)

The placement of resistors is a tradeoff. If the resistor is in the LED leg, the current in the LEDs is well controlled. Even a short across one LED will not cause an excessive spike.

A resistor in series with the input to the capacitor limits the amount of inrush current to charge the capacitor. If all of the resistance is outside the LED loop, there is a risk that shorting one LED will produce a large current spike through the LEDs, possibly damaging them. The resistor will decrease the voltage to which the capacitor charges.

I haven't played with LED lighting circuits yet to determine values, but I expect that you would need different values of resistance depending upon where the resistors are placed. That is why I didn't include any values with my schematic. I would appreciate information from anyone experimenting with these circuits. The 20 mA target for LED current would seem to be appropriate for most common LEDs.

(One of my constraints is that I run mostly conventional. This circuit does not provide any regulation over a range of track voltage, but that isn't a problem in Command mode.)
Just curious before I go and rewire another fleet of cars for LED lighting.

I have some K-Line transit passenger cars the big long ones.
The lights are too bright and if I run 8 passenger cars it trips the breaker.

If I were to rewire the cars top to bottom lighting board for in Series wiring instead of parallel, this will reduce the light to a better level at full volts (DCS/TMCC full track power)
But would it cut the current being used??

I have done this on several cabooses with interior lights to bright and they are just the right brightness now!

I have a few fleets of passenger cars to rewire when time to reduce the current draw and bright lights, big project.
quote:
Originally posted by kj356:
Just curious before I go and rewire another fleet of cars for LED lighting.

I have some K-Line transit passenger cars the big long ones.
The lights are too bright and if I run 8 passenger cars it trips the breaker.

If I were to rewire the cars top to bottom lighting board for in Series wiring instead of parallel, this will reduce the light to a better level at full volts (DCS/TMCC full track power)
But would it cut the current being used??

I have done this on several cabooses with interior lights to bright and they are just the right brightness now!

I have a few fleets of passenger cars to rewire when time to reduce the current draw and bright lights, big project.


6 LEDs in series would pull 20 ma (.02 amps) For a 24 volt input that is about 1/2 watt. In this circuit in conventional the LEDs would dim as do light bulbs with the throttle. In command they would not dim except for variation in track voltage due to voltage drop.

6 LEDs wired in parallel would pull about 3 watts at 24 volts or 6 times as much. Still the 3 watt pull is much less than light bulbs. With a regulated circuit the bulbs will not dim with throttle in conventional. In conventional the 3 watt pull is reduced as the throttle is reduced. At 12 volts for example the pull would be 1.5 watts,with less heat generated by the CL2N3 chip or 7805 regulator at the lower voltage. Various wiring configurations for LEDs are on my blog with pictures in the link below. Which one to use depends on how you run your trains.

http://www.jcstudiosinc.com/Bl...tegoryMain?catId=426

If the LEDs are too bright they can be dimmed by using a larger value resistor than minimum. An adjustable pot can be installed also.

Dale M thank you for the explanation.

Dale H
Mine actually provide pretty good light down to about 11 volts of track voltage, I have a CL2, and two of the three LED sections in each car. I did jumper out the 130 ohm resistors on the strips to lower the operating voltage. but they work very well.

I do strictly command/control. so having sufficient voltage isn't really an issue. I also use a bridge rectifier and a filter cap to get a bit more voltage at the inputs.

I have to add a choke for the DCS operation for my one DCS locomotive, since it's the one that will be pulling these cars! Big Grin

I will say that those light strings are great and very easy to use. I'm going to order more of them for some other passenger cars, they're great!
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